Weather and Garden: Wind Chill, Heat Index and Watering
The numbers behind the weather and a thriving garden — how wind chill and heat index work, what dew point tells you, when each becomes dangerous, and how to water and harvest rain.
Dew Point Calculator
Verified formula Updated Jun 2026 Private — runs on your device
Verified formula
Private
Dew point (approx.)
17.0
For general information only — not financial, tax, legal or medical advice. Verify before you rely on it.
How to use the Dew Point Calculator
The Dew Point Calculator works out your dew point (approx.) in an instant. Enter air temperature and relative humidity and the result updates as you type — it is free, needs no sign-up, and runs entirely in your browser so your figures stay private.
- Enter the air temperature.
- Enter the relative humidity.
- Read off your dew point (approx.) — the calculator updates automatically, with no button to press.
Formula
The Dew Point Calculator uses the formula:
Dew point (approx.) = Air temperature - (100 - Relative humidity) ÷ 5
Worked example
For example, with air temperature of 25 °C and relative humidity of 6%, the dew point (approx.) is 17.0.
| Air temperature | 25 °C |
|---|---|
| Relative humidity | 6% |
| Dew point (approx.) | 17.0 |
|---|
Results are estimates for educational use, not professional advice.
Frequently asked questions
It is the temperature at which air becomes saturated and dew forms. At 25°C and 60% humidity it is about 17°C.
It uses the quick rule: dew point ≈ temperature − (100 − humidity) ÷ 5, accurate for humidity above about 50%.
A higher dew point feels muggier and signals more moisture in the air. Above about 20°C it feels quite humid.
Relative humidity changes with temperature, while dew point is an absolute measure of moisture that does not change as air warms or cools.
The Dew Point Calculator uses the formula: Dew point (approx.) = Air temperature - (100 - Relative humidity) ÷ 5. For example, with air temperature of 25 °C and relative humidity of 6%, the dew point (approx.) is 17.0.
Enter the air temperature. Enter the relative humidity. Read off your dew point (approx.) — the calculator updates automatically, with no button to press.
Related guides
Dew Point Table: Dew point (approx.) by Air temperature
Reference table of dew point (approx.) for Dew Point across a range of air temperature values — exact, engine-computed figures you can read off at a glance.
How to Calculate Dew Point: Formula, Steps & Examples
Learn how to calculate Dew Point — the formula explained step by step, with worked examples and a free calculator to check your answer.
Heat Index Table: Heat index (feels like) by Temperature
Reference table of heat index (feels like) for Heat Index across a range of temperature values — exact, engine-computed figures you can read off at a glance.